The basic lift pump was developed to bring subsurface liquids to the surface. A typical lift pump contains a standing valve and a traveling valve each comprised of a ball and a seat. When the lift pump makes a down stroke, the tubing which contains the traveling valve is lowered relative to the casing in which the standing valve is mounted. The resulting fluid pressure raises the ball of the traveling valve, allowing fluid to enter the tubing. During the subsequent up stroke, the tubing is raised, the ball falls into the traveling valve seat and fluid is trapped inside the tubing. The pressure inside the casing drops, causing fluid to enter the casing by raising the standing valve ball off of the standing valve seat. The succeeding down stroke of the lift pump again lowers the tubing, increasing the pressure in the casing. The standing valve ball drops into the standing valve seat, thereby sealing the interior of the casing, and the traveling valve opens permitting more fluid to enter the tubing.
This process exposes both the standing valve and the traveling valve to considerable deterioration. For instance, sand or corrosive materials contained in the fluid can gradually destroy the ball of each valve. Another problem involves uncontrolled movement of the traveling valve ball inside the tubing and the standing valve ball inside the casing. Deterioration of either ball results in an imperfect seal between that ball and its respective valve seat, thus allowing fluid to leak out of the casing or the tubing. As a result, costly repairs are frequently needed during which the pump is out of operation. Protecting the standing valve ball and the traveling valve ball from the corrosive materials and the sand and grit present in the well fluid and preventing uncontrolled movement of both balls inside the casing and the tubing considerably increases the working life of both the standing valve and the traveling valve and high efficiency is maintained without the frequent, costly repairs and the resulting down time.
According to the present invention, the increase in fluid pressure below the traveling valve which occurs when the tubing is lowered into the casing causes a piston situated just below the traveling valve seat to rise. The piston lifts the traveling valve ball out of the traveling valve seat. A protector shield contains and protects the traveling valve ball from the fluid flow and uncontrolled movement inside the tubing while the traveling valve is open. Likewise, when the tubing is raised the drop in pressure inside the casing causes a similar piston to lift the standing valve ball out of the standing valve seat. A second protection shield contains and protects the standing valve ball from fluid flow and uncontrolled movement inside the casing while the standing valve is open.